使用组前缀进行Laravel测试

I have a group for api:

Route::group(array('prefix' => 'api'), function () {

    Route::get('abc', function () {
        return 'abc';
    });
  );

But, when testing use $this->call('GET', '/api/abc) or $this->call('GET', 'path_to_abc'), I always get 404 error, although I've printed the url and I can visit that link on browser

If you haven't configured your TestCase.php file, you need to set your app url there as

File: TestCase.php

 /**
 * The base URL to use while testing the application.
 *
 * @var string
 */
protected $baseUrl = 'http://YOUR_APP_URL';